Not a good advice if your friends group are the same sex with you, which tends to be the case for a lot of people.

You gotta fish where the fish are.

Like, if you're unemployed and you want a job, you don't first go out making friends, hoping that once you become friends one of them can give you a job. You get a job by looking for a job and applying to jobs. Sure, depending on where you live and who you engage with you, might luck out and meet someone who can have a job for you but that's not the norm and you don't want to leave your survival to that random chance.

Similarly, if you want a romantic relationship you need to engage in dating activities specifically designed to maximize the protentional of meeting a romantic partner, not in friend making activities hoping one of them will be your next romantic partner because you might be wasting a lot of time with no returns.

Actually, I think the opposite is better: Engaging in dating activates can actually net you some friends along the way if the romantic part doesn't click.